Dio Chrysostom quotes
[ Diogenes] was surprised by the fact that had he claimed to be a physician for the teeth, everybody would flock to him who needed to have a tooth pulled; yes, and by heavens, had he professed to treat the eyes, all who were suffering from sore eyes would present themselves, and similarly, if he had claimed to know of a medicine for diseases of the spleen or for gout or for running of the nose; but when he declared that all who should follow his treatment would be relieved of folly, wickedness, and intemperance, not a man would listen to him or seek to be cured by him, ... as though it were worse for a man to suffer from an enlarged spleen or a decayed tooth than from a soul that is foolish, ignorant, cowardly, rash, pleasure-loving, illiberal, irascible, unkind, and wicked, in fact utterly corrupt.
Dio Chrysostom